Every calculator on this site shows its working. This page lists the exact formulas, the assumptions behind them, the worked examples we check on every build, and where each figure comes from — so you can verify our maths instead of taking it on trust.

How each calculator computes

• USDA Loan Calculator (homepage). Loan amount = (home price − down payment) × 1.01 when the 1% upfront guarantee fee is financed. Monthly principal & interest uses the standard amortisation formula on that loan amount. The monthly USDA fee = current balance × 0.35% ÷ 12, recalculated as the balance falls — never on the original balance. Property tax, homeowners insurance and HOA dues are added as entered.
• Income Eligibility Checker. USDA limit = area median income (AMI) × 115%. Adjusted income = annual income − ($480 × dependents under 18) − reasonable childcare costs − $525 (once, if the household includes an elderly 62+ or disabled member). The verdict compares adjusted income, not gross income, with the limit.
• Guarantee Fee Calculator. Upfront fee = loan × 1%. Annual fee each month = outstanding balance × 0.35% ÷ 12. Lifetime total = upfront fee + every year of annual fee over the term. The year-by-year table uses the same amortisation as the homepage, so the fee falls as the balance falls.
• USDA vs FHA vs Conventional vs VA. Same home price, same rate, 30-year term on all four. USDA: 0% down, 1% upfront, 0.35% annual. FHA: 3.5% down, 1.75% upfront (UFMIP), 0.55% annual MIP. Conventional: 3% down, no upfront fee, PMI estimated at 0.50% a year (an assumption — real PMI depends on credit score and down payment, typically 0.3–1.5%). VA: 0% down, 2.15% one-time funding fee for first use, no monthly fee.
• Affordability / DTI Checker. Front-end ratio = monthly housing payment ÷ gross monthly income (guideline 29%). Back-end ratio = (housing payment + all other monthly debts) ÷ gross monthly income (guideline 41%).
• Refinance Calculator. New loan = current balance + 1% upfront guarantee fee when financed. Monthly saving = current principal & interest − new principal & interest (both 30-year). Break-even = closing costs ÷ monthly saving.
• Property Eligibility Rules. A six-question first-pass check against the published USDA rules. It cannot verify an address — only the official USDA eligibility map can, and the page links to it.

Worked examples we check on every build

Before any change goes live, we re-run these cases and confirm the calculators still produce them:

• $350,000 home, 0% down, 6.25%, 30 years, $3,150/year tax, $1,800/year insurance, 1% fee financed: loan $353,500, principal & interest $2,176.56, annual fee $103.10 in month one, taxes $262.50, insurance $150.00 — $2,692.16 per month.
• $300,000 loan: upfront guarantee fee $3,000; annual fee $88.38 a month in year one when financed ($303,000 × 0.35% ÷ 12).
• Income: $128,000 gross, two dependents ($960) and $8,000 childcare → deductions $8,960 → $119,040 adjusted income.
• Fee decline: on a $300,000 loan the annual fee falls every year as the balance falls — the guarantee fee page’s year-by-year table shows each year’s figure, and the last year’s monthly fee is only a few dollars.

Assumptions and limitations

• Fixed rate, on-time payments. All calculators assume a fixed interest rate and payments made on time for the full term.
• Guaranteed loans only. Every calculator on this site covers USDA Single Family Housing Guaranteed loans (private lender + USDA guarantee, 1%/0.35% fees). USDA Direct loans are a different program (USDA itself lends, lower incomes, subsidised rates, no guarantee fees) and are not modelled here.
• The annual fee never cancels. The USDA 0.35% annual fee runs for the life of the loan. Only refinancing into a conventional loan removes it.
• Rates are averages, not quotes. The default rate is a published national average (see below), not a rate any lender has offered you. Your rate depends on your credit, the lender and the day you lock.
• Taxes and insurance are your inputs. Property tax and homeowners insurance vary by county and home; the defaults are examples, not estimates for your property.
• Estimates only. Nothing here is a loan offer, a guarantee of approval, or financial advice. Your lender’s figures control.

Why our deduction figures are $480 and $525

USDA’s income rule (7 CFR 3555.152(c)) does not set the deduction dollar amounts itself — it points to HUD’s definition of adjusted income at 24 CFR 5.611. That regulation currently sets $480 per dependent and $525 for an elderly or disabled family, adjusted by HUD annually for inflation. Older USDA training material (2020) quoted $400 for the elderly deduction — that was the figure before the Housing Opportunity Through Modernization Act (HOTMA) raised it. Some web pages quote $500 per dependent and $550 for elderly households; we could not find those figures in the current regulation or in HB-1-3555 Chapter 9, so we do not use them. If the regulation changes, this page and the income calculator will be updated together.

How figures stay current

Once a month we check: the default interest rate (Optimal Blue USDA 30-year average, cross-checked against the Freddie Mac Primary Mortgage Market Survey); the guarantee fee schedule (FY2027: 1% upfront, 0.35% annual, 1 Oct 2026 – 30 Sep 2027); and the income limits (FY2026 standard: $122,800 for 1–4 people / $162,100 for 5–8 people, effective 13 July 2026). Every change updates the “Last updated” date on the affected pages. The default rate as of 13 November 2026 is 7.02% (Optimal Blue USDA 30-year average, 12 Nov 2026); Freddie Mac’s 30-year average was 7.18% in the week of 5 Nov 2026.

Sources

• USDA Rural Development — Single Family Housing Guaranteed Loan Program
• USDA Income and Property Eligibility Site (official map)
• USDA income limits tool
• USDA Guaranteed Housing Program income limits (HB-1-3555, Appendix 5) — FY2026 limits, revised 13 July 2026
• USDA Handbook HB-1-3555 (PDF)
• HB-1-3555, Chapter 9: Income Analysis (PDF, revised 5 Aug 2025)
• 7 CFR 3555.107 — guarantee fee
• 7 CFR 3555.152 — income eligibility and adjusted income
• 24 CFR 5.611 — adjusted income ($480 per dependent; $525 elderly/disabled family)
• Consumer Financial Protection Bureau — How to review your Loan Estimate
• Optimal Blue USDA 30-year average rate (7.02%, 12 Nov 2026, as published there)

FHA mortgage insurance figures follow HUD Mortgagee Letter 2023-05 (1.75% upfront; 0.55% annual for most 30-year loans under 5% down). VA funding fee figures follow the VA’s 2026 schedule (2.15% first use at 0% down; 3.30% subsequent use; exempt for veterans receiving VA disability compensation).

Who runs this site

This is an independent calculator project, run as a small website — not a lender, broker, or government agency, and not affiliated with the U.S. Department of Agriculture. No loan officer or lending credential is claimed for anyone here: the figures are checked against USDA publications (listed above), not based on any individual’s lending experience, and every tool page links its sources so you can check them yourself. Found an error? Email hello@usdaloanscalculator.com — corrections are fixed and re-dated.